Our 12 Year Old Son Has Had These Weird White

Our 12 year old son has had these weird white rashy bumps at the nape of his neck over the last week - week and a 1/2. He says they aren’t itchy. We have not been able to figure out what it is. We put hydrocortisone on it and it dried up the bumps and they got scabby. But now, as we were giving him a haircut we noticed they are all over his scalp. Again, he says they don't itch or hurt. Is it possible it's from a new helmet he has been wearing for sports?